Field of the Invention
The present invention concerns a method for recording a magnetic resonance dataset of at least one foreign body in a target region of a patient, as well as and to a magnetic resonance apparatus designed to implement such a method.
Description of the Prior Art
In surgical procedures, foreign bodies may be introduced into a patient. While implants are a classic example of such foreign bodies, glues, fillings, foreign-material fastenings, cementations and other, possibly functional, medical devices must also be mentioned. If such a foreign body is introduced into a patient or produced in the patient, complications often occur, for example rejection reactions by the body, infections or mechanical faults leading to the loss of the structural integrity and/or the functionality of the foreign body. For example, cemented implants may not integrate correctly in the relevant bones or may fail by becoming detached after successful implantation. Polymeric fastenings, glues and cements may become defective due to degradation over time, for example crack formation and such like. Biodegradable devices such as retaining screws may fail in their intended function due to inflammatory responses in patients or to breakage. In order to be able to intervene in good time in such a case of failure, for example in order to prevent irreparable damage, accurate detection and characterization of the functional state of the foreign body is necessary.
For application cases of this kind, in which a non-invasive evaluation of the foreign body, for example an implant, is desirable, imaging modalities such as computed tomography and ultrasound are less suitable, because image artifacts often occur, the contrast is unsuitable and inflammations or such like do not become visible. In principle, magnetic resonance imaging is therefore an obvious choice as an imaging modality, since it provides high signal and contrast resolution of soft tissues and bones, but it has not been capable of visualizing the integrity of foreign bodies, for example solid implants and fastening components. Magnetic resonance imaging normally cannot be used because the magnetic resonance signal has already decayed before the current magnetic resonance sequences could measure it. In addition, pronounced image artifacts can occur, because metallic foreign bodies, in particular, can distort the fields of the magnetic resonance scanner that are necessary for measurement, due to their susceptibility effects. While magnetic resonance sequences that reduce these artifacts and permit imaging of the tissue around the foreign body have become known, no method for imaging the foreign bodies themselves, which is suitable for extensive clinical practice, has yet become known.